Despite the "demographic imperative" of a rapidly increasing older US population and rising cancer rates with advancing age, there is a shortage of researchers trained to address the growing cancer control needs of this heterogeneous older age group. Dr. Mandelblatt is one of the few scientists in the US with this expertise. In the current application, Dr. Mandelblatt seeks to renew her Senior Cancer Control Scientist Award to develop new research paradigms and mentor the next generation of scientists focused on improving cancer outcomes for the growing older population. In the first four years of this award the candidate has made considerable progress in developing new research on chemotherapy decisions and mentoring junior investigators as evidenced by competing for 4 new peer-reviewed grants and continuing 1 grant, publishing more than 40 high profile publications, integrating research on older women into national cancer screening guidelines, mentoring 9 investigators, and facilitating mentored faculty in their publication of 59 papers and receipt of 19 new grant awards. This high level of progress would not have been possible without the protected time afforded by the original award. The goals for this new award are to: 1) contribute new knowledge about the risks of and outcomes from use of systematic adjuvant therapy in older women with breast cancer by: a) using data from an established cohort of older women to understand how systemic treatment affects quality of life, b) conducting new research to develop an index of "physiological age" to predict toxicity of chemotherapy among older breast cancer patients, and c) incorporating these data into existing simulation models to inform clinical and policy efforts to enhance the quality and cost-effectiveness of care for older women, 2) to maintain databases from research projects and make them available to trainees for the conduct of new studies about variations in breast cancer treatment, toxicity, and outcomes, and 3) to train and support young investigators. Overall, Dr. Mandelblatt is an established researcher who has demonstrated a sustained, high level of research and mentoring productivity. She has made important scientific contributions to the field and has made outstanding progress in the first grant period. Continuation of this award will allow Dr. Mandelblatt to have sufficient protected time to train new investigators and develop new research innovations to advance the science of cancer control at the intersection of aging.